Automobile Black Boxes
By Perry Zucker
Submitted April, 2003
For many years "Black Boxes" were synonymous with airplane crashes. The acquired (downloaded) data from these boxes were an invaluable tool for accident investigative engineers.
In the early 70's, the National Transportation Safety Board (NTSB) made
several recommendations that the automobile manufacturers (OEM) and National
Highway Traffic Safety Administration (NHTSA) gather data on crashes using
onboard sensing and recorders. As a direct result certain air bag equipped
vehicles had recorders incorporated within.
Electronic sensors are gaining wide use in today's vehicles, which are primarily driven by the automobile industry's move towards electronically controlled systems. Through various methods (algorithms), these systems gather information (data) about the vehicle. Onboard computers (Electronic Control Module / OBD I / II) allowed the technician to check the operation of the engines and other vital components.
As the design of supplement restrain system (SRS - air bags), anti-lock brakes (ABS) and stability control systems, additional sensors and processors were needed. These new ECM's were capable of storing data, which includes resultants of fault errors. Henceforth, the "Black Box" was born.
All vehicles that are equipped with airbag(s) have three (3) basic components. They are as follows:
The Bag is construct of a woven material similar to nylon, which is folded like a parachute. They are coated with talc like powder that lubricates the air bag material for storage.
The Inflation System is similar to a solid rocket booster. This solid material ignites which burns extremely hot and rapidly to create gas. This action inflates the nitrogen gas (pulsed) via a chemical reaction of sodium azide (NaN3) and potassium nitrate (KNO3).
The Sensor is an electrical and/or mechanical device, which triggers a firing squib that activates the inflation systems and deploys the airbag(s).
The on-board computer's (ECM / OBD I / II) data is stored in two types of categories. They are as follows:
Non-Deployment Incident is an event that is severe enough to gather information from the sensors but NOT severe enough to deploy the air bag(s).
Deployment Incident is an event that is severe enough to gather information from the sensors and to deploy the air bag(s).
In both types of incidents the vehicle's processor (RAM) stores in memory, pre and post crash data.
The "Black Box" can record informational data, such as: engine / vehicle speed (5 seconds before impact), brake status (5 seconds before impact), throttle position(s), and even the state of the driver's seat belt switch (on/off). The combination of this information along with other engineering factors will indeed revolutionize the field of motor vehicle accident investigation.
About the Author: Perry J. Zucker, Degreed Engineer (several degrees in engineering as well as technology), provides technical reports, pre-trial preparation, and expert witness testimony concerning vehicle related accidents (reconstruction), traffic violations, general accidents, and product liability cases, for both plaintiffs / defendants and civil / criminal. He is a member of SAE, IEEE, ASME, State Appellate Div. Expert Panel, ASE certified, State vehicle inspector and a certified speed measuring device operator / instructor. His office can be reached at (718) 375-5063 or visit him on the web at trafficdoc.com.
Copyright © 2003 Perry Zucker.All rights reserved. No portion of this article may be reproduced without the express written permission of the copyright holder. If you believe you may lawfully use a quotation, excerpt or paraphrase of this article under the Fair Use exception to copyright law, except as otherwise authorized by the author of the article, you must cite this article as a source for your work and include a link back to the original article from any online materials that incorporate or are derived from the content of this article.